37 CFR § 41.41 - Reply brief.
(a) Timing. Appellant may file only a single reply brief to an examiner's answer within the later of two months from the date of either the examiner's answer, or a decision refusing to grant a petition under § 1.181 of this title to designate a new ground of rejection in an examiner's answer.
(1) A reply brief shall not include any new or non-admitted amendment, or any new or non-admitted affidavit or other Evidence. See § 1.116 of this title for amendments, affidavits or other evidence filed after final action but before or on the same date of filing an appeal and § 41.33 for amendments, affidavits or other Evidence filed after the date of filing the appeal.
(2) Any argument raised in the reply brief which was not raised in the appeal brief, or is not responsive to an argument raised in the examiner's answer, including any designated new ground of rejection, will not be considered by the Board for purposes of the present appeal, unless good cause is shown.
(c) Extensions of time. Extensions of time under § 1.136(a) of this title for patent applications are not applicable to the time period set forth in this section. See § 1.136(b) of this title for extensions of time to reply for patent applications and § 1.550(c) of this title for extensions of time to reply for ex parte reexamination proceedings.